Autonomously guided missiles such as air to air and surface to air guided missiles are frequently used in the military field for attacking targets such as jet aircraft, helicopters, armoured vehicles and ships, and are normally equipped with infrared homing heads for direction-finding and tracking of the target. In order to provide defense against such guided missiles with infrared homing heads, aircraft use a wide range of different electronic and pyrotechnic countermeasures, such as infrared jammers and infrared decoys, which imitate the infrared signature of the target in order to spoof the approaching guided missiles. These countermeasures are matched, in particular, to the characteristics of aircraft, in particular specifically to their engines.
Specific countermeasures for protection of land-based and surface-vessel platforms, such as tanks and ships, against attacking guided missiles with infrared homing heads must likewise be matched to the characteristic features of the target. By way of example, ships are comparatively cool targets (Tmax=200° C.), so their maximum emission occurs in the spectral range between 8 and 14 μm while, in contrast, jet aircraft in particular have maximum emission levels in the range from 2 to 5 μm. A further difference from aircraft is the low relative speed of ships and the large surface area, the large surface area emitting infrared radiation (200 to 2000 m2 for ships in comparison to 20 to 50 m2 for aircraft). Furthermore, the surface area which emits the infrared radiation is considerably contoured and also has short-wave emission maxima (so-called hot spots) which may be caused by particularly hot parts such as the funnel and the catapult launcher.
FIG. 1 shows the beam strength distribution for a grey emitter 1 and a black-body emitter 2 for an assumed body temperature of 473° K. The abscissa shows the wavelength in μm. The ordinate shows the beam strength in mW cm−2 μm−1. Owing to the illustrated characteristic for the selective emitter, guided weapons with imaging two-colour infrared homing heads in the ranges 2 to 5 μm and 8 to 14 μm are preferably used for attacking ships.